Tritone substitution progressions
The tritone substitution is a relative common feature in especially jazz. How this feature are used and why is explained by various analyzed examples.
Tritone is the name of the interval made up of three whole steps. For example C to G# (Ab) or G to C# (Db).
Substitution means that a chord is substituded (replaced) for another that normally isn't involved. For example is G7 often followed by C7, but by suing a tritone substitution C7 would insted be C#7 in this case. This change can also be written as I7 - #V7.
Some examples of a progression inclduing a tritone substitution:
C7 - G#7 (G#7 is the tritone substitution chord)
D7 - A#7 (A#7 is the tritone substitution chord)
E7 - C7 (C7 is the tritone substitution chord)
G7 - C#7 (C#7 is the tritone substitution chord)
In a song the tritone substitution may consist of a half bar and it could look like this:
C#7 can be seen as the tension chord that is resolved by C7 before turning home to the I chord.
Or as a part of a turnaround:
Here, C#7 replaces the more expected D7.
The tritone substitution can also be used in a progression with a chromatic motion:
Dm7 – C#7 – Cmaj7 (iim7 – #I7 – Imaj7)
ii - V - I with tritone substitutions in all keys
The V chord is substituted for another V chord, which root is a tritone interval away.
Only seventh chords are mentioned in the table and in other examples, but it is possible to use 9th and 13th chords instead as well as altered chords.